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Abstract:

A method and an Evolved Node Base-station (eNB) for avoiding an
occurrence of a ping-pong handover between adjacent cells are provided.
The eNB comprises: a statistics module, a storage module, a judging
module and a parameter adjusting module. The method includes: during a
statistics period, eNBs serving two adjacent cells involved in a
ping-pong handover, making a statistics on times of the serving cell of
the eNB being used as a source cell and a target cell in a second
handover in a process of each ping-pong handover occurring between the
two adjacent cells respectively; upon the end of the statistics period,
if the eNB determines that the times of the serving cell of the eNB being
used as the source cell in the second handover is greater than the times
of as the target cell, the eNB increasing a value of a handover control
parameter of this serving cell.

Claims:

1. A method for avoiding an occurrence of a ping-pong handover between
adjacent cells, comprising: during a statistics period, an evolved Node B
(eNB) serving two adjacent cells firstly determining the occurrence of
the ping-ping handover between the two adjacent cells, and then making a
statistics on times of the serving cell of the eNB being used as a source
cell and a target cell in a second handover in a process of the ping-pong
handover respectively; upon an end of the statistics period, if the eNB
determines that the times of the serving cell of the eNB being used as
the source cell in the second handover is greater than the times of being
used as the target cell, the eNB increasing a value of a handover control
parameter of the serving cell of the eNB.

2. The method according to claim 1, wherein, in said step of determining
the occurrence of the ping-ping handover between the two adjacent cells,
if the eNB of the two adjacent cells judges that a user equipment (UE)
has handed over between the two adjacent cells continuously for three
times within a duration of a ping-pong judging threshold value, the UE is
believed to be undergoing a ping-pong handover between the two adjacent
cells.

3. The method according to claim 2, wherein, said step of determining the
occurrence of the ping-ping handover between the two adjacent cells
comprises: A. when the eNB knows that the UE has handed over from or
handed over to the serving cell of the eNB, the eNB judging according to
a history information cell of the UE whether former two handovers of the
UE both occur between the two cells involved in this handover, if yes,
executing step B; if not, executing step C; B. judging whether a sum of
residing durations of the UE in each cell after the former two handovers
is less than or equal to a preset ping-pong judging threshold value, if
yes, it is believed that this handover and the former two handovers
constitute a ping-ping handover of the UE between the two adjacent cells;
if not, executing step C; C. the eNB continuing to wait for the UE to
report a handover-to or handover-from notifying message, and executing
step A after receiving the notifying message.

4. The method according to claim 2, wherein, the process that the UE has
handed over between the two adjacent cells continuously for three times
includes following two scenes: Scene A: the UE continuously hands over
between the two adjacent cells, a cell 1 and a cell 2, wherein the UE
hands over from the cell 1 to the cell 2 for two times, and hands over
from the cell 2 to the cell 1 once; Scene B: the UE continuously hands
over between the cell 1 and the cell 2, wherein the UE hands over from
the cell 2 to the cell 1 for two times, and hands over from the cell 1 to
the cell 2 once; in said step of the eNB making the statistics on the
times of the serving cell of the eNB being used as the source cell and
the target cell in the second handover in the process of the ping-pong
handover during the statistics period, the eNB makes a statistics on
times of occurrences of Scene A and Scene B in the statistics period for
the UE.

5. The method according to claim 1, wherein, the eNB is configured with a
step length; said step of the eNB increasing the value of the handover
control parameter of the serving cell of the eNB comprises: adding the
step length to the original handover control parameter.

6. The method according to claim 1, wherein, the method further
comprises: presetting an adjusting determination parameter Δ in the
eNB; when the eNB judges that the times of the serving cell of the eNB
being used as the source cell in the second handover is greater than the
times of being used as the target cell, the step of the eNB increasing
the value of the handover control parameter of a local cell comprises:
the eNB increasing the value of the handover control parameter of the
local cell when the eNB judges that the times of the serving cell of the
eNB being used as the source cell in the second handover is greater than
a sum of the times of being used as a target cell and Δ.

7. The method according to claim 6, further comprising: the eNB
increasing the value of the handover control parameter of the serving
cell of the eNB when the eNB judges that an absolute value of a
difference between the times of the serving cell of the eNB being used as
the target cell and the times of being used as the source cell in the
second handover is less than Δ.

8. The method according to claim 6, further comprising: the eNB not
adjusting the value of the handover control parameter of the serving cell
of the eNB when the eNB judges that the times of the serving cell of the
eNB being used as the target cell in the second handover is greater than
a sum of the times of being used as the source cell and Δ.

9. The method according to claims 1, wherein, the handover control
parameter includes any one of Time to Trigger, Hysteresis, Cell
Individual Offset, and Threshold, and any combination thereof.

10. An Evolved Node B (eNB) for avoiding an occurrence of a ping-pong
handover between adjacent cells, comprising: a statistics module, a
storage module, a judging module and a parameter adjusting module; the
statistics module is configured to make an statistics on times of the
serving cell of the eNB being used as a source cell and a target cell in
a second handover in a process of each ping-pong handover occurring
between the cell and an adjacent cell, and updating the times to the
storage module; the storage module is configured to store information
about the times counted by the statistics module and a value of a
handover control parameter of the serving cell; the judging module is
configured to send a parameter increasing command to the parameter
adjusting module if it is judged upon an end of the statistics period
that the times of the serving cell being used as the source cell in the
second handover is greater than the times of being used as the target
cell; the parameter adjusting module is configured to increase the value
of the handover control parameter of the serving cell stored in the
storage module after receiving the parameter increasing command.

11. The eNB according to claim 10, wherein, the statistics module is also
configured to determine that a user equipment (UE) is undergoing the
ping-pong handover between the serving cell and the adjacent cell if it
is judged that the UE has handed over between the two adjacent cells
continuously for three times within a duration of a ping-pong judging
threshold value.

12. The eNB according to claim 11, wherein, a process that the UE has
undergone three handovers between the two adjacent cells continuously
includes following two scenes: Scene A: the UE continuously hands over
between two adjacent cells, a cell 1 and a cell 2, wherein the UE hands
over from the cell 1 to the cell 2 for two times, and hands over from the
cell 2 to the cell 1 once; Scene B: the UE continuously hands over
between the cell 1 and the cell 2, wherein the UE hands over from the
cell 2 to the cell 1 for two times, and hands over from the cell 1 to the
cell 2 once; the statistics module is configured to makes a statistics on
times of occurrences of Scene A and Scene B in the statistics period for
the UE.

13. The eNB according to claim 10, wherein, the parameter adjusting
module is configured with a step length; the parameter adjusting module
is configured to add the step length to the original handover control
parameter stored in the storage module upon receiving the parameter
increasing command.

14. The eNB according to claim 10, wherein, the judging module is
configured with an adjusting determination parameter Δ; the judging
module is configured to send the parameter increasing command to the
parameter adjusting module when it is judged that the times of the
serving cell being used as the source cell in the second handover is
greater than a sum of the times of being used as the target cell and
Δ.

15. The eNB according to claim 14, wherein, the judging module is also
configured to send the parameter increasing command to the parameter
adjusting module when it is judged that an absolute value of a difference
between the times of the serving cell being used as the target cell and
the times of being used as the source cell in the second handover is less
than Δ.

16. The method according to claim 3, wherein, the process that the UE has
handed over between the two adjacent cells continuously for three times
includes following two scenes: Scene A: the UE continuously hands over
between the two adjacent cells, a cell 1 and a cell 2, wherein the UE
hands over from the cell 1 to the cell 2 for two times, and hands over
from the cell 2 to the cell 1 once; Scene B: the UE continuously hands
over between the cell 1 and the cell 2, wherein the UE hands over from
the cell 2 to the cell 1 for two times, and hands over from the cell 1 to
the cell 2 once; in said step of the eNB making the statistics on the
times of the serving cell of the eNB being used as the source cell and
the target cell in the second handover in the process of the ping-pong
handover during the statistics period, the eNB makes a statistics on
times of occurrences of Scene A and Scene B in the statistics period for
the UE.

17. The method according to claim 7, further comprising: the eNB not
adjusting the value of the handover control parameter of the serving cell
of the eNB when the eNB judges that the times of the serving cell of the
eNB being used as the target cell in the second handover is greater than
a sum of the times of being used as the source cell and Δ.

18. The method according to claims 5, wherein, the handover control
parameter includes any one of Time to Trigger, Hysteresis, Cell
Individual Offset, and Threshold, and any combination thereof.

19. The method according to claims 6, wherein, the handover control
parameter includes any one of Time to Trigger, Hysteresis, Cell
Individual Offset, and Threshold, and any combination thereof.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a Long Term Evolution (LTE)
communication system, and in particular, to a method and an Evolved Node
Base-station (eNodeB, eNB) for avoiding occurrence of ping-pong handover
between adjacent cells.

BACKGROUND ART

[0002] Mobility management is an important attribute in a mobile
communication system, and handover is a key part of mobility management,
since a reasonable handover act can decrease spending made by the system
to realize mobility.

[0003] In a LTE system, the state of a User Equipment (UE) can be
RRC_CONNECTED and RRC_IDLE. When a UE in RRC_CONNECTED state moves from a
serving cell to another cell, it will trigger a cross-cell handover in
order to ensure continuity of the services.

[0004] During the process of the handover, the UE firstly measures the
currently serving cell and the adjacent cell according to a measurement
control message issued by the Evolved Node B (eNB) in the LTE system, and
processes and analyzes the measurement result according to the handover
control parameters in the measurement control message, and if the
handover condition is satisfied, then it reports the handover event to
the eNB, and the eNB then prepares and executes the handover. In this
process, the configuration of the handover control parameter determines
whether the time of handover occurrence is suitable or not, if the
parameter is configured to be too low and the handover condition can be
easily satisfied, then ping-pong handover between the serving cell and
the target cell is apt to occur. Ping-pong handover increase the spending
of the communication system for ensuring mobility of the user, and thus
should be avoided as far as possible.

[0005] The current method for avoiding ping-pong handover is: when a UE
successfully hands over from a cell 1 to a cell 2, the eNB starts a timer
Tpingpong; before the timer Tpingpong times out, if the eNB
receives a measurement event report, in which the event type is handover
and the target cell is the cell 1, reported by the UE again, then the eNB
discards the report, that is, it does not originate handover act to the
cell 1. When the timer Tpingpong times out, if the eNB receives a
measurement event report with the target cell being the cell 1, reported
by the UE again, and the handover condition is satisfied, it is allowed
to originate the handover act to the cell 1.

[0006] This kind of processing means begins with limiting the handover act
of a single UE, which seemingly limits the probability of the occurrence
of ping-pong handover, but actually does not reduce the possibility of
occurrence of ping-pong handover radically.

[0007] In the meantime, the way of using a timer has a problem--there is a
high requirement on configuration of the duration of the timer. If the
duration is configured to be too short, then ping-pong handover cannot be
efficiently controlled; if the duration is configured to be too long,
then it may lead to the result that the UE cannot hand over back to the
original serving cell in time after the handover if the quality of the
target cell is too bad, thus causing a call drop. As shown in FIG. 1, the
arrow indicates the moving direction of the user, and after the users
hands over from a cell 1 to a cell 2, the second handover back to the
cell 1 in a short time period is reasonable, but the method in the prior
art limits such a correct handover act, which may cause a call drop due
to untimely handover.

SUMMARY OF THE INVENTION

[0008] The technical problem to be solved in the present invention is to
provide a method and Evolved Node B (eNB) for avoiding occurrence of
ping-pong handover between adjacent cells, so as to avoid ping-pong
handover between two adjacent cells due to improper configuration of the
handover parameter (i.e., then handover criterion can be easily
satisfied).

[0009] In order to solve the above problem, the present invention provides
a method for avoiding occurrence of ping-pong handover between adjacent
cells, comprising the following steps of:

[0010] during a statistics period, an eNB serving two adjacent cells
firstly determining an occurrence of a ping-ping handover between the two
adjacent cells, and then making statistics on the times of a serving cell
of the eNB being used as a source cell and a target cell in a second
handover in a process of each ping-pong handover occurring between the
two adjacent cells respectively;

[0011] upon end of the statistics period, if the eNB determines that the
times of the serving cell of the eNB being used as a source cell in the
second handover is greater than the times of being used as a target cell,
the eNB increasing a value of a handover control parameter of the serving
cell of the eNB.

[0012] The above method may be also characterized in that:

[0013] in said step of determining an occurrence of a ping-ping handover
between the two adjacent cells, if the eNB of the two adjacent cells
judges that a user equipment (UE) has handed over between the two
adjacent cells continuously for three times within a duration of a
ping-pong judging threshold value, the UE is considered to be undergoing
a ping-pong handover between the two adjacent cells.

[0014] The above method may be also characterized in that:

[0015] said step of determining an occurrence of a ping-ping handover
between the two adjacent cells comprises:

[0016] A. when the eNB knows that the UE has handed over from or handed
over to the serving cell of the eNB, the eNB judging, according to a
history information cell of the UE, whether the former two handovers of
the UE both occur between the two adjacent cells involved in this
handover, if yes, executing step B; if not, executing step C;

[0017] B. judging whether a sum of the residing durations of the UE in
each cell after the former two handovers is less than or equal to a
preset ping-pong judging threshold value, if yes, it is considered that
this handover and the former two handovers constitute a ping-ping
handover of the UE between the two adjacent cells; if not, executing step
C;

[0018] C. the eNB continuing to wait for the UE to report a handover-to or
handover-from notifying message, and executing step A after receiving the
notifying message.

[0019] The above method may be also characterized in that:

[0020] the process that the UE has handed over between the two adjacent
cells continuously for three times includes the following two scenes:

[0021] Scene A: the UE continuously hands over between two adjacent cells,
a cell 1 and a cell 2, wherein the UE hands over from the cell 1 to the
cell 2 for two times, and hands over from the cell 2 to the cell 1 once;

[0022] Scene B: the UE continuously hands over between the cell 1 and the
cell 2, wherein the UE hands over from the cell 2 to the cell 1 for two
times, and hands over from the cell 1 to the cell 2 once;

[0023] then in said step of the eNB making statistics on the times of the
serving cell of the eNB being used as a source cell and a target cell in
a second handover in a process of a ping-pong handover during a
statistics period, the eNB makes statistics on the times of the
occurrences of Scene A and Scene B in the statistics period for the UE.

[0024] The above method may be also characterized in that:

[0025] the eNB is configured with a step length;

[0026] said step of the eNB increasing the value of the handover control
parameter of the serving cell of the eNB comprises: adding the step
length to the original handover control parameter.

[0027] The above method may be also characterized in that:

[0028] the method further comprises: presetting an adjusting determination
parameter Δ in the eNB;

[0029] when the eNB judges that the times of the serving cell of the eNB
being used as a source cell in the second handover is greater than the
times of being used as a target cell, the step of the eNB increasing the
value of the handover control parameter of the local cell comprises: the
eNB increasing the value of the handover control parameter of the local
cell when the eNB judges that the times of the serving cell of the eNB
being used as a source cell in the second handover is greater than a sum
of the times of being used as a target cell and Δ.

[0030] The method further comprises:

[0031] the eNB increasing the value of the handover control parameter of
the serving cell of the eNB when the eNB judges that an absolute value of
a difference between the times of the serving cell of the eNB being used
as a target cell and the times of being used as a source cell in the
second handover is less than Δ.

[0032] The method further comprises:

[0033] the eNB not adjusting the value of the handover control parameter
of the serving cell of the eNB when the eNB judges that the times of the
serving cell of the eNB being used as a target cell in the second
handover is greater than a sum of the times of being used as a source
cell and Δ.

[0034] The above method may be also characterized in that:

[0035] the handover control parameter includes any one of Time to Trigger,
Hysteresis, Cell Individual Offset, and Threshold, and any combination
thereof.

[0036] In order to solve the above problem, the present invention further
provides an Evolved Node Base-station (eNB) for avoiding occurrence of
ping-pong handover between adjacent cells, comprising: a statistics
module, a storage module, a judging module and a parameter adjusting
module;

[0037] the statistics module is configured to make statistics on times of
the serving cell of the eNB being used as a source cell and a target cell
in a second handover in a process of each ping-pong handover occurring
between the cell and an adjacent cell, and updating the times to the
storage module;

[0038] the storage module is configured to store information about the
times counted by the statistics module and a value of a handover control
parameter of the serving cell;

[0039] the judging module is configured to send a parameter increasing
command to the parameter adjusting module if it is judged upon end of a
statistics period that the times of the serving cell being used as a
source cell in the second handover is greater than the times of being
used as a target cell;

[0040] the parameter adjusting module is configured to increase the value
of the handover control parameter of the serving cell stored in the
storage module after receiving the parameter increasing command.

[0041] The above eNB is also characterized in that:

[0042] the statistics module is also configured to determine that a user
equipment (UE) is undergoing a ping-pong handover between the serving
cell and an adjacent cell when judging that the UE has handed over
between the serving cell and the adjacent cell continuously for three
times within a duration of a ping-pong judging threshold value.

[0043] The above eNB is also characterized in that:

[0044] the process that the UE has undergone three handovers between the
two adjacent cells continuously includes the following two scenes:

[0045] Scene A: the UE continuously hands over between two adjacent cells,
a cell 1 and a cell 2, wherein the UE hands over from the cell 1 to the
cell 2 for two times, and hands over from the cell 2 to the cell 1 once;

[0046] Scene B: the UE continuously hands over between the cell 1 and the
cell 2, wherein the UE hands over from the cell 2 to the cell 1 for two
times, and hands over from the cell 1 to the cell 2 once;

[0047] the statistics module is configured to makes statistics on times of
occurrences of Scene A and Scene B in the statistics period for the UE.

[0048] The above eNB is also characterized in that:

[0049] the parameter adjusting module is configured with a step length;

[0050] the parameter adjusting module is configured to add the step length
to the original handover control parameter stored in the storage module
upon receiving the parameter increasing command.

[0051] The above eNB is also characterized in that:

[0052] the judging module is configured with an adjusting determination
parameter Δ;

[0053] the judging module is configured to send a parameter increasing
command to the parameter adjusting module when it is judged that the
times of the serving cell being used as a source cell in the second
handover is greater than a sum of the times of being used as a target
cell and Δ.

[0054] The above eNB is also characterized in that:

[0055] the judging module is also configured to send a parameter
increasing command to the parameter adjusting module when it is judged
that an absolute value of a difference between the times of the serving
cell being used as a target cell and the times of being used as a source
cell in the second handover is less than Δ.

[0056] In regard to the ping-pong handover problem caused by improper
configuration of the handover control parameter of the cell, the present
invention can identify and position the cell whose parameter needs to be
optimized, and can reduce the possibility of occurrence of ping-pong
handover radically by means of adjusting the handover parameter of the
cell (for example, the Cell Individual Offset), thereby reducing the
expenses for the system to realize mobility and optimizing the whole
network. Meanwhile, with the self-optimization technique, the present
invention can automatically implement scene identification and parameter
adjustment, thereby greatly reducing manpower input in the previous
network for operation maintenance and making the network operation more
conveniently.

BRIEF DESCRIPTION OF DRAWINGS

[0057] FIG. 1 exemplifies the scene of a ping-pong handover in the prior
art;

[0058]FIG. 2 illustrates identifying a ping-pong handover according to an
example of the present invention;

[0059] FIG. 3 illustrates specific scene A and scene B for a ping-pong
handover according to an example of the present invention;

[0060] FIG. 4 illustrates the method of making statistics on scene A and
scene B for a continuous ping-pong handover according to an example of
the present invention;

[0061] FIG. 5 illustrates adjusting the handover parameter according to
the times of scene A and scene B according to an example of the present
invention;

[0062] FIG. 6 illustrates the structure of an eNB for avoiding occurrence
of ping-pong handover between adjacent cells according to an example of
the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

[0063] The technical scheme of the present invention will be further
described in detail below with reference to the attached drawings and
examples.

[0064] The basic concept of the present invention is as follows: during a
statistics period, eNBs, which serve two adjacent cells involved in a
ping-pong handover, make statistics on times of the serving cell of the
eNBs being used as a source cell and a target cell in a second handover
in a process of each ping-pong handover occurring between the above two
adjacent cells respectively; upon end of the statistics period, if the
eNB determines that the times of the serving cell of the eNB being used
as a source cell in the second handover is greater than the times of
being used as a target cell, the eNB increases a value of a handover
control parameter of the local cell. Wherein, the handover control
parameter includes many aspects, for example, Time to Trigger,
Hysteresis, Cell Individual Offset, and Threshold which can all be used
as objects of the adjustment.

[0065] As shown in FIG. 2, in a LTE system, when a UE hands over between
the cells, the eNB of the source cell will send the history information
of the UE (UE History Info) to the eNB of the target cell, and the cell
of UE History Info mainly comprises a list of cells the UE has accessed
in the last several times (including the Global Cell Identity (GCI) of
the cell that has been accessed), and the residing durations in the above
various cells. As shown in FIGS. 2, T1, T2 and T3 are residing durations
of the UE in various cells, and the eNB can acquire the handover record
of the UE according to the UE History Info.

[0066] Ping-pong handover can be defined as a case in which a user hands
over between two adjacent cells continuously for many times within a
short period of time. Therefore, the specific flow of the eNBs of the two
adjacent cells respectively judging whether the UE is undergoing a
ping-pong handover between the two adjacent cells includes:

[0067] 1. When the eNB knows that the UE has handed over from or handed
over to the serving cell of the eNB, the eNB judges, according to a
history information cell of the UE, whether the former two handovers of
the UE both occur between the two adjacent cells involved in this
handover, if yes, executing step 2; if not, executing step 3;

[0068] 2. It is judged whether a sum of a residing duration of the UE in
each cell after the former two handovers is less than or equal to a
preset ping-pong judging threshold value (i.e., judging whether the sum
of T2 and T3 in FIG. 2 is less than the preset ping-pong judging
threshold value), if yes, it is considered that this handover and the
former two handovers constitute a ping-ping handover of the UE between
the two adjacent cells; if not, executing step 3;

[0069] 3. The eNB continuing to wait for the UE to report a handover-to or
handover-from notifying message, and executing step 1 after receiving the
notifying message.

[0070] It can be seen from the above judging flow that if the eNBs of the
two adjacent cells judge that the UE has handed over between the two
adjacent cells continuously for three times within the duration of the
ping-pong judging threshold value, the UE is considered to be undergoing
a ping-pong handover between the two adjacent cells.

[0071] As shown in FIG. 3, the process that the UE has three handovers
continuously between the two adjacent cells includes the following two
scenes:

[0072] Scene A: the UE continuously hands over between a cell 1 and a cell
2, wherein the UE hands over from the cell 1 to the cell 2 for two times,
and hands over from the cell 2 to the cell 1 once; in this ping-pong
handover process, the cell 1 is used as a target cell in the second
handover, and the cell 2 is used as a source cell;

[0073] Scene B: the UE continuously hands over between a cell 1 and a cell
2, wherein the UE hands over from the cell 2 to the cell 1 for two times,
and hands over from the cell 1 to the cell 2 once; in this ping-pong
handover process, the cell 2 is used as a target cell in the second
handover, and the cell 1 is used as a source cell.

[0074] Therefore, in the inventive concept, the step of the eNBs making a
statistics on times of the serving cell of the eNB being used as a source
cells and a target cell in a second handover in a process of each
ping-pong handover occurring between the two adjacent cells respectively
during a statistics period can be specifically making the statistics on
the times of the occurrences of Scene A and Scene B in the statistics
period for the UE.

[0075] It can be seen that with regard to the cell 1, if the eNB serving
the cell identifies that Scene A occurs currently, the eNB serving the
cell 2 is sure to be able to identify the occurrence of Scene B, and vise
versa, that is, the following formulas are satisfied:

Number of Scenes A in cell 1=Number of Scenes B in cell 2

Number of Scenes B in cell 1=Number of Scenes A in cell 2

[0076] If more than three continuous handovers have occurred, a statistics
is made according to the method as shown in FIG. 4, i.e., for the cell 1,
the former three handovers constitute Scene A, and the second through to
the fourth handover constitute Scene B.

[0077] In specific implementation, a step length may be configured in the
eNB, and increasing the handover control parameter of the serving cell of
the eNB may be specifically adding the step length on the basis of the
original handover control parameter.

[0078] In order to facilitate controlling of the process of adjusting the
handover control parameter, the eNB may be also configured with a preset
adjusting determination parameter (Δ), and when the eNB determines
that the times of the serving cell of the eNB being used as the source
cell in the second handover (i.e., the times of occurrence of Scene A) is
greater than the times of being used as the target cell (i.e., the times
of occurrence of Scene B), the eNB increasing the value of a handover
control parameter of the serving cell of the eNB may be specifically
implemented as:

[0079] the eNB increases the value of the handover control parameter of
the local cell when the eNB judges that the times of the serving cell of
the eNB being used as the source cell in the second handover is greater
than a sum of the times of being used as the target cell andΔ.
Correspondingly, the eNB increases the value of the handover control
parameter of the serving cell of the eNB when the eNB judges that an
absolute value of a difference between the times of the serving cell of
the eNB being used as the target cell and the times of being used as the
source cell in the second handover is less thanΔ; in other cases,
the eNB does not adjust the value of the handover control parameter of
the serving cell of the eNB.

[0080] Description will be made below with two application examples of the
present invention.

[0081] The parameters involved in the present example include: statistic
period (T), ping-pong judging threshold (Thresh), adjusting determination
parameter (Δ), handover control parameter and parameter adjusting
step length. In a specific example, the method specifically used will be
exemplarily described in terms of Cell Individual Offset and Hysteresis.
It is regulated in protocol TR36.331 V850 that the adjusting step length
for Hysteresis is 0.5 dB, and the adjusting step length for Cell
Individual Offset is 1 dB in the range of [-6 dB˜6 dB]. Other
parameters can be set specifically in specific implementations so as to
change the granularity of the algorithm. The steps for carrying out the
present invention and the difference in using different handover control
parameters will be described below with reference to the examples.

Example 1

[0082] It is assumed that the statistics period is one day, the ping-pong
judging threshold is 5s, the parameter adjusting determination parameter
is Δ, the counter for counting the Scene A in cell 1 is A, and the
counter for counting the Scene B is B.

[0083] The eNB serving the cell 1 mainly observes the following two kinds
of users:

[0084] 1) the user in the cell 1, from which the eNB side receives a
measurement report and determines a handover, with the target cell being
the cell 2;

[0085] 2) the user that receives a handover-to request message with the
handover source cell being the cell 2.

[0086] As for the use in 1), judgment is made according to the history
information of the user stored in the eNB and the residing duration of
the user in the cell 1 currently.

[0087] If the list of history cells in the history information is cell 2,
cell 1, and the sum of the residing duration in cell 2 and the residing
duration in cell 1 currently is less than or equal to 5s, then it is
judged that a ping-pong handover occurs currently, and the counter A for
the Scene A in cell 1 is added with 1.

[0088] As for the user in 2), a judgment is made according to the history
information in the handover-to request message received from the user.

[0089] If the list of history cells in the history information is cell 2,
cell 1, cell 2, and the sum of the residing duration in cell 2 and the
residing duration in cell 1 is less than or equal to 5s, then it is
judged that the ping-pong handover occurs currently, and the counter B
for the Scene B in cell 1 is added with 1.

[0090] Through the above counting method, the statistics of Scene A and
Scene B after one day is observed:

[0091] if A>B+Δ, then no processing is implemented;

[0092] if B>A+Δ, then the Cell Individual Offset in cell 1
corresponding to cell 2 is added with 1 dB; if |A-B|<Δ, then the
Cell Individual Offset in cell 1 corresponding to cell 2is added with 1
dB.

[0093] The statistics of Scene A and Scene B counted during the present
statistics period is cleared, and the statistics of Scene A and Scene B
during the next period is observed continually.

[0095] It is assumed that the statistics period is one day, the ping-pong
judging threshold is 5s, the parameter adjusting determination parameter
is Δ, the four adjacent cells in cell 1 have four pairs of counters
for Scene A and Scene B, i.e., A12 and B12, A13 and B13, A14 and B14, A15
and B15, which are used to make the statistics on the ping-pong handover
act between cell 1 and a certain corresponding adjacent cell.

[0096] The eNB of the cell 1 observes the following two kinds of users for
the cell pair composed of cell 1 and each adjacent cell (assuming in the
current cell pair, cell 1 and cell 2 are observed):

[0097] 1) the user in the cell 1, from which the eNB side receives a
measurement report and determines a handover, with the target cell being
the cell 2;

[0098] 2) the user that receives a handover-to request message with the
handover source cell being the cell 2.

[0099] As for the use in 1), a judgment is made according to the history
information of the user stored in the eNB and the residing duration of
the user in the cell 1 currently.

[0100] If the list of history cells in the history information is cell 2,
cell 1, and the sum of the residing duration in cell 2 and the residing
duration in cell 1 currently is less than or equal to 5s, then it is
judged that the ping-pong handover occurs currently, and the counter
A12 for the Scene A in cell 1 corresponding to the adjacent cell 2
is added with 1.

[0101] As for the user in 2), a judgment is made according to the history
information in the handover-to request message received from the user.

[0102] If the list of history cells in the history information is cell 2,
cell 1, cell 2, and the sum of the residing duration in cell 2 and the
residing duration in cell 1 is less than or equal to 5s, then it is
judged that the ping-pong handover occurs currently, and the counter
B12 for the Scene B in cell 1 corresponding to the adjacent cell 2
is added with 1.

[0103] Through the above counting method, the statistics is made on
A13 and B13, A14 and B14, A15 and B15
respectively. Each of counters A1x and B1x is observed in one
day, and the judging result may be divided into the following three
cases:

A1x>B1x+Δ; 1)

B1x>A1x+AΔ 2)

|A1x-B1x|<Δ. 3)

[0104] If case 1) is present, as for cell X that satisfies the two cases
of 2) and 3), the Cell Individual Offset in cell 1 corresponding to the
cell X is added with 1 dB.

[0105] If case 1) is not present, and all adjacent cells satisfy case 2)
or case 3), then the Hysteresis in cell 1 is added with a step length,
0.5 dB.

[0106] The statistics of Scene A and Scene B counted during the present
statistics period is cleared, and the statistics of Scene A and Scene B
during the next period in cell 1 corresponding to each adjacent cell
respectively is observed continually.

[0107] In addition, as shown in FIG. 6, the eNB for avoiding the
occurrence of the ping-pong handover between the adjacent cells provided
in the present invention comprises a statistics module, a storage module,
a judging module and a parameter adjusting module;

[0108] the statistics module is used to make statistics on times of the
serving cell of the eNB being used as a source cell and a target cell in
a second handover in a process of each ping-pong handover occurring
between the cell and an adjacent cell, and updating the times to the
storage module;

[0109] the storage module is used to store information about the times
counted by the statistics module and a value of a handover control
parameter of the serving cell;

[0110] the judging module is used to send a parameter increasing command
to the parameter adjusting module if it is judged upon end of a
statistics period that the times of the serving cell being used as the
source cell in the second handover is greater than the times of being
used as the target cell;

[0111] the parameter adjusting module is used to increase the value of the
handover control parameter of the serving cell stored in the storage
module after receiving the parameter increasing command.

[0112] Furthermore, the statistics module is also used to determine that a
user equipment (UE) is undergoing the ping-pong handover between the
serving cell and an adjacent cell if it is judged that the UE has handed
over between the two adjacent cells continuously for three times within a
duration of a ping-pong judging threshold value.

[0113] The process that the UE has undergone three handovers between the
two adjacent cells continuously includes the following two scenes:

[0114] Scene A: the UE continuously hands over between two adjacent cells,
a cell 1 and a cell 2, wherein the UE hands over from the cell 1 to the
cell 2 for two times, and hands over from the cell 2 to the cell 1 once;

[0115] Scene B: the UE continuously hands over between the cell 1 and the
cell 2, wherein the UE hands over from the cell 2 to the cell 1 for two
times, and hands over from the cell 1 to the cell 2 once;

[0116] Then the statistics module being used to make the statistics on the
times of the serving cell of eNB being used as the source cell and the
target cell in a second handover in a process of each ping-pong handover
occurring between the cell and an adjacent cell is specifically: the
statistics module being used to make the statistics on the times of the
occurrences of Scene A and Scene B in the statistics period for the UE.

[0117] The parameter adjusting module is configured with a step length;

[0118] The parameter adjusting module being used to increase the value of
the handover control parameter of the serving cell stored in the storage
module after receiving the parameter increasing command is specifically:
the parameter adjusting module being used to add the step length to the
original handover control parameter stored in the storage module upon
receiving the parameter increasing command.

[0119] The judging module is preset with an adjusting determination
parameter Δ;

[0120] The judging module being used to send the parameter increasing
command to the parameter adjusting module if it is judged upon the end of
the statistics period that the times of the serving cell being used as
the source cell in the second handover is greater than the times of being
used as the target cell is specifically: the judging module being used to
send the parameter increasing command to the parameter adjusting module
when it is judged that the times of the serving cell being used as the
source cell in the second handover is greater than a sum of the times of
being used as the target cell and Δ.

[0121] The judging module is also used to send the parameter increasing
command to the parameter adjusting module when it is judged that an
absolute value of a difference between the times of the serving cell
being used as the target cell and the times of being used as the source
cell in the second handover is less than Δ.

[0122] Of course, the present invention may have many other examples, and
a person having ordinary skill in the art can make various corresponding
modifications and transformations according to the present invention
without departing from the sprit and essence of the present invention.
These corresponding modifications and transformations, however, shall be
within the protection scope defined by the claims of the present
invention.

INDUSTRIAL APPLICABILITY

[0123] In regard to the ping-pong handover problem caused by improper
configuration of the handover control parameter of the cell, the present
invention can identify and position the cell whose parameter needs to be
optimized, and can reduce the possibility of the occurrence of the
ping-pong handover radically by means of adjusting the handover parameter
of the cell (for example, the Cell Individual Offset), thereby reducing
the expenses for the system to realize mobility and optimizing the whole
network. Meanwhile, with the self-optimization technique, the present
invention can automatically implement scene identification and parameter
adjustment, thereby greatly reducing manpower input in the previous
network for operation maintenance and making the network operation more
conveniently.